Note: I set the Line-in as the capture channel for audio and mute it, so that no real-time audio coming out of the speaker. After 20 secs sleep, the recording playback started, settings to 5 secs is too low & the playback may stop itself.

To determine alsa hardware ID (hw.0,0) – assuming audio card 0 is the one
that connected the tv card audio out through line-in

$ amixer -c 0

Check

Simple mixer control 'Input Source',0
...
Item0: 'Line'

Therefore, device ID is 0 (see ‘Input Source’)

ALSA hardware ID : hw.<cardID>,<deviceID>

To record:

$ chmod +x rekodtv.sh
$ ./rekodtv.sh

To force stop the recording (above script will auto stop record after 60 minutes)